Burner assembly

ABSTRACT

A gas-fired furnace including a heat exchanger mounted in a housing in heat transfer relation with flowing air passing over the heat transfer surface of the heat exchanger and a gas burner assembly; the heat exchanger having a centrally disposed burner tube communicating with a rear tube sheet at one end and the gas burner assembly at the opposite end, and a plurality of return tubes disposed about the burner tube and affixed to the rear tube sheet at one end and a flue gas collector at the opposite end.

United States Patent 91 Mutchler Apr. 3, 1973 [54] BURNER ASSEMBLY [75]Inventor: Paul A. Mutchler, University City,

[73] Assignee: American Air Filter Company, Inc.,

Louisville, Ky.

[22] Filed: Nov. 24, 1971 [21] Appl. No.; 201,879

[52] US. Cl. ..431/352, 431/353, 126/116,

239/405 [51] Int. Cl ..F23d 13/40 [58] Field of Search ..43l/l82, 185,351, 352, 353; 239/405, 406

[5 6] References Cited UNITED STATES PATENTS 3,178,161 4/1965 Yeo etal...43l/351 llllli 10/1935 Theunissen ..43l/352 9/1972 Reich ..43l/353Primary Examiner-William E. Wayner Assistant Examiner-William E.Tapolcai, Jr. Att0rneyRalph B. Brick [57] ABSTRACT A gas-fired furnaceincluding a heat exchanger mounted in a housing in heat transferrelation with flowing air passing over the heat transfer surface of theheat exchanger and a gas burner assembly; the heat exchanger having acentrally disposed burner tube communicating with a rear tube sheet atone end and the gas burner assembly at the opposite end, and a pluralityof return tubes disposed about the burner tube and affixed to the reartube sheet at one end and a flue gas collector at the opposite end.

5 Claims, 5 Drawing Figures P/JENHZUH'N I97 3,724,995 SHEET 1 OF 3 IN VEN TOR.

M101 AME/11m imam/5n MZ M Pmmenm ms sum 2 UF 3 IN VEN TOR. BY PM Mum [RBURNER ASSEMBLY BACKGROUND OF THE INVENTION This invention relates to agas-fired furnace and more particularly to a novel tube-type heatexchanger and gas burner assembly, the gas burner assembly beingadaptable for cooperating with the novel heat exchanger.

In previous forced draft burner constructions for gasfired furnaceshaving horizontal return tubes, high velocity nozzles from smalldiameter burner blast tubes have been used to fire into rectangularrefractory combustion chambers or, unnecessarily large cylindricalfurnace tubes. In accordance with the present invention it is recognizedthat these high velocity flows often have a tendency to cause momentaryblowoff of the flame at the burner blast tube end and the gas fires thatare late in developing their maximum heat release have tended to makelittle use of the direct heating surface near the burner or firing endof the furnace. The present invention further recognizes that these latedeveloping gas fires also have led to overworking and overheating of therear tube sheet which causes for short life and early failure of therear tube sheet and the horizontal return tube end where the tubes jointhe rear tube sheet. Moreover, it is recognized that full advantage hasnot been made of the primary heating surface of the furnace therebymaking it necessary to operate a gas burner with minimum excess air inorder to keep the stack temperature down to a level necessary to achievethe required furnace efficiency.

SUMMARY OF THE INVENTION The present invention, recognizing thedisadvantages of previous gas-fired furnaces, provides a novel methodfor burning gaseous fuels with a broad base flame while developing afire very quickly. Furthermore, the burner of the present inventionprovides means for establishing a flame having a slow forward velocitywhile at the same time releasing its heat very quickly.

The present invention advantageously provides. a straightforwardarrangement for the preparation of a gas-fired furnace.

The present invention further provides a novel gas burner assembly foruse in gas-fired furnaces.

Various other features of the present invention will become obvious tothose skilled in the art upon reading the disclosure set forthhereinafter.

More particularly, the present invention provides a gas-fired furnacecomprising:

A. a housing having an air inlet and an air outlet;

B. the housing including a heat exchanger and a gasfired burnerassembly, the burner assembly having a central opening therein;

C. the heat exchanger including a burner tube of relatively largecross-sectional area and being adapted to receive heated gas from theburner assembly, the burner tube having an inlet and an outlet and beingin axial alignment with and in communication with the opening of theburner assembly at the inlet and a rear tube sheet at the outlet, therear tube sheet having an opening therein of generally the samecross-sectional area as the inside of the burner tube communicating withthe burner tube outlet, at least one second opening in the rear tubesheet communicating with flue gas return means, the flue gas returnmeans being in communication with a flue gas collector, the flue gasreturn means being adapted to receive heated gas from the burner tube atthe rear tube sheet transferring the gas to the flue gas collector;

D. the flue gas collector having a flue gas outlet;

E. a combustion air inlet and a fuel gas inlet, the combustion air inletand the fuel gas inlet being in communication with the gas burnerassembly; and,

F. expansion means in communication with the burner tube whereby uponcontraction and expansion of the burner tube the openings in the burnertube remain generally stationary.

Even more particularly, the present invention provides a gas burnerassembly comprising: a burner housing having fuel and air inlet meansand an outlet, the housing defining a plenum therein; a longitudinallyextending chamber of serrated configuration adapted to be receivedwithin the housing, the chamber having a plurality of generally V-shapedpockets therein, each pocket being defined by each serration; a gas ringmanifold adapted to be received within the housing, the manifold havingan inlet in communication with the fuel inlet means in the housing and aplurality of apertures spaced in axial alignment with the pockets of theserrated configured chamber whereby fuel enters the chamber through thepockets parallel to the axis of the chamber; and, each V-shaped pocketincludes two flanks, at least one of the flanks having at least oneaperture therein whereby air entering the plenum through the air inletin the housing passes through the aperture in the flank transversely ofthe fuel passing through the V-shaped pocket.

It is to be understood that the description of the examples of thepresent invention given hereinafter are not by way of limitation.Various modifications within the scope of the present invention willoccur to those skilled in the art upon reading the disclosure set forthhereinafter.

' Referring to the drawings:

FIG. 1 is a cross-sectional view of a gas-fired furnace of the presentinvention;

FIG. 2 is an enlarged exploded perspective view of a gas burner assemblyof FIG. 1 without a burner hous- FIG. 3 is another enlarged explodedperspective view of the gas burner assembly of FIG. 1 includingexpansion means with certain portions thereof cutaway;

FIG. 4 is an enlarged plan view of the expansion means of FIG. 1 withphantom lines indicating the position of the expansion means uponexpansion and contraction of the burner tube; and,

FIG. 5 is an enlarged perspective view of the front end of the gas-firedfurnace of FIG. 1.

FIG. 1 illustrates a gas furnace 1 including a gas burner assembly 3 ofthe present invention. The gas furnace 1 includes a housing 2 having aninlet 4 for air which is to be heated in the furnace l and an outlet 6for the discharge of the heated air. Means for introducing air to beheated is not shown but may include any means known in the'prior art,such as, for example, a blower.

The gas furnace l is further provided with a heat exchanger 7, the heatexchanger 7 including a plurality of elongated tubes 8 of relativelysmall cross-sectional area disposed about an enlarged cylinder or burnertube 9 of relatively large cross-sectional area with the tubes 8 beingaffixed at one end to a flue gas collector l1 and at the other end to arear tube sheet 12. The burner tube 9 is joined to the rear tube sheet12 at one end and a flexible expansion flange or heat 19 at the otherend, the head 19 being attached to a corrugated collar 13, collar 13being connected to the front tube sheet 14 of the flue gas collector 11.The flexible expansion head 19 being disposed between the burner tube 9and the corrugated collar 13 is incorporated to relieve the expansionand contraction of the burner tube 9 as the temperature of the burnertube 9 fluctuates over a wide temperature range. It is realized that anexpansion means, such as flexible expansion head 19, may be adapted forpositioning between the burner tube and the rear tube sheet in additionto or in lieu of the aforementioned exemplified position of the flexibleexpansion head 19. The front tube sheet 14 of the collector 11 has anaperture 16 therein which is generally of the same diameter as thediameter of the corrugated collar 13 for axial alignment therewith.Further, burner assembly 3 is provided with an aperture 17 (FIG. 3) ofgenerally the same diameter as the corrugated collar 13 and the aperture17 is also adaptable for axial alignment with collar 13.

In FIGS. 2 and 3 the gas burner assembly 3 of the present inventionincludes housing 21 defining a combustion air plenum with combustion airinlet 22 and fuel gas inlet 23 disposed therein. The housing 21 isadapted to enclose a longitudinally extending cylindrical shaped chamber25 having a plurality of serrated sections 28 along the peripheralboundary of the chamber 25 and a fuel gas manifold distribution ring 24axially aligned with the chamber 25. The longitudinally extendingcylindrical shaped chamber 25 is determined by a flange or burnermounting plate 30 flxedat one end thereof and having an aperture 17therein and a front closure plate 26 fixed at the other end, plate 26having serrated edges for aligning with the serrated sections 28 of thechamber 25.

The serrated sections or interior pockets 28 of generally V-shapedcross-section are determined by a plurality of flanks 29 and 31 at leasteach of the flanks 31 having combustion air inlet apertures 27 disposedtherein. The front plate 26 is provided with a plurality of apertures 42therein along the serrated edges for communication with the interiorpockets 28, apertures 42 serving to permit the introduction of fuel gasinto the pockets 28 of the chamber 25. In operation, fuel gas passesthrough apertures 42 from the fuel gas distribution ring 24 (in a mannerdescribed hereinafter) parallel to the longitudinal axis of the chamber25 into individual pockets 28 of the chamber 25 and combustion airenters into pockets 28 tranversely of the fuel gas through apertures 27in flanks 31 to develop a flame in each pocket 28. There are generally aplurality of apertures 27 for each flank 31 for uniform distributing ofcombustion air throughout each pocket 28. Front plate 26 is furtherprovided with a plurality of auxiliary combustion air inlets 43 in theform of radially extending slots and a conduit 44 for receiving a pilotgas assembly (not shown), the pilot gas assembly being constructed byany conventional method. The auxiliary air inlets 43 are spacedinteriorly of the apertures 42 providing additional combustion airparallel to the iongitudinal axis of chamber 25, the additionalcombustion air being available as the flame being developed in theserrated pockets 28 moves tangentially toward the center of the chamber25.

The fuel gas manifold distribution ring 24 includes fuel gas inletconduit 23 and a plurality of fuel gas outlets 33, the fuel gas outlets33 adapted to be aligned with the fuel gas inlets 42 of the front plate26. Flange 32 including the fuel gas outlets 33 is adapted forcommunication with the outer periphery of the front closure plate 26 andis affixed to the plate 26 by any known method, such as bolting,welding, and the like.

In assembling the gas burner assembly 3 to the corrugated collar 13, aflange 18 is provided on the inlet to the corrugated collar 13 withapertures 38 therein. Front tube sheet 14 includes apertures 34 thereinfor alignment with apertures 38 of the collar 13 and apertures 37 in theburner mounting plate 30 of the gas assembly 3; apertures 37, 34, and 38being in axial alignment to receive bolts 36 therethrough, bolts 36being inserted through apertures 38, 34, and 37 with washers 39 and nuts41 being inserted thereon for holding gas assembly 3 in fluid tightcommunication with the corrugated collar 13 with the front tube sheet 14being disposed therebetween. Burner housing 21 encircling the gas burnerassembly 3 is then affixed to the front tube sheet 14 by means notshown, such as, welding, bolting, and the like.

FIG. 4 illustrates the operation of the annular flexible head 19surrounding burner tube 9 and fixed along its inner circumferencethereto when the burner tube 9 expands and contracts during heat up andcool down of the furnace. Phantom lines illustrate that as the tube 9expands and contracts the corrugated collar 13 remains intact, annularflexible head 19 changing its position with movement of the burner tube9. The collar 13 in the example is of corrugated configuration toimprove the strength at the juncture of the burner tube 9 and the fluegas collector 11. It is realized that the corrugated collar 13 may bedesigned with deeper corrugations to allow for expansion andcontraction, thereby relieving stresses in the furnace, alleviating theneed for the flexing head 19. However, if the inside diameter of thecollar 13 is relatively small in relation to the outside diameter of thetube 9, a thin gauge stainless steel material may be used as the flexhead 19 to give sufficient flexibility for relieving stresses caused bythe expansion and contraction of the tube 9. For example, it has beenfound that for a collar 13 of 8-inch ID and a burner tube of 16-inch OD,a flex head 19 of 20 gauge 316 type stainless steel is sufficient formost applications.

FIG. 5 illustrates in detail the front end of the exemplified gas-firedfurnace of the present invention showing the flow of air across the unitto best utilize the heat transfer surface of the heat exchanger. Aspointed out previously, return tubes 8 are attached to the front tubesheet 14, lower return tubes 8a being disposed beneath the burnerhousing 21 and the upper return tubes 8b being disposed above the burnerhousing 21. The flue gas collector 11 is illustrated as a plenum ofgenerally C-shaped cross-section whereby the flue gas return from thelower return tubes 8a being collected in the lower portion of thecollector 1 1 passes upwardly along the side of the housing 21 beforemixing with the flue gas from the upper return tubes 8b. It is notedthat by allowing the hot flue gases to pass upwards along the side ofthe housing 21 it is advantageous for good heat transfer to introducethe air to be heated in the heat exchanger at a point so that it willcontact the upwardly extending heat surface 45, surface 45 beingdisposed between the upwardly moving hot flue gases and the generallyhorizontally moving relatively cold air.

The front end of the gas-fired furnace is further provided with aZ-shaped configured partition 46 as one side of the housing 21separating the combustion air plenum 5 (FIG. 3) from the flue gascollector 11. The Z-shaped partition 46 is attached at one end to thewall 47 of housing 21 and the front tube sheet 14 at the other. Thepartition 46 is of Z-shaped configuration to allow movement of the tubesheet 14 upon expansion and contraction of return tubes 8 during heat upand cool down of the furnace.

In the operation of the gas-fired furnace 1 of the present invention,pilot fuel gas and pilot combustion air are brought into the gas burnerassembly 3 through conduit 44 wherein the pilot gas mixture is ignitedby means not shown, such as, for example, electrode means, these meansof ignition of a pilot gas-air mixture being any known in the prior art.Combustion air is introduced into the assembly 3 from combustion airblower 40 (FIG. 5) through inlet 22 in housing 21 and apertures 27 inthe cylindrical shaped chamber 25, the air being directed transverselyto the flow of fuel in each pocket 28 of the chamber 25, the fuel gasbeing brought in through the ring 24 by way of fuel gas conduit 23 andin turn passes through the ring 24 and out by way of the apertures 33which are in alignment with the apertures 42 in the cylindrical shapedchamber 25. The pilot gas-air mixture ignites the fuel gas-air mixturein each pocket 28, the gas flame being developed in each pocket havingtangential direction toward the center of the chamber 25. Further,additional combustion air is fed interiorally of the chamber 25 throughradially slotted apertures 43 for further mixing and ignition of thefuel gas. Ignition of the fuel gas-air mixture in pockets 28 firstlyenables the firing of a mixture rich in fuel gas at these locationstherebyproviding smooth and safe light offs while the gas flame beingdeveloped has tangential direction toward the center of the chamber 25.The gas flame developed in this manner has a broad base and a very slowforward velocity and when entering the burner tube 9 allows for almostmaximum heat release early in the cylinder or heat exchanger. It isfurther realized that because of the initial firing of gas-air mixturerich in fuel gas the burner assembly 3 of the present invention does notrequire a gas-air premix before the gas is discharged into theindividual gas burning pockets 28 so the burner can use raw gas forcombustion purposes. The combustion gases upon leaving the burnerassembly 3 flow through the corrugated collar 13 and into the burnertube 9, rear tube sheet 12, plenum 15, and then to the flue gascollector collar 1 l by way of the elongated tubes 8. The combustiongases leave the furnace through flue gas outlet 10 in the flue gascollector collar 1 l.

The air to be processed or heated by the heat exchanger enters thefurnace 1 through inlet 4 being moved therethrough by means not shown,such as a blower, circulating through the housing 2 in heat transferrelationship with he heat exchanger 7. The

heated air then leaves the furnace through the housing air outlet 6.

It is realized that various changes may be made to the specificembodiment shown and described without departing from the scope andspirit of the present invention.

What is claimed is:

1. In a gas-fired furnace, a gas burner assembly comprising: a burnerhousing having fuel and air inlet means and an outlet, said housingdefining a plenum therein; a longitudinally extending chamber ofserrated configuration adapted to be received within said housing, saidchamber having a plurality of generally V- shaped pockets therein, eachpocket being defined by each serration; a gas ring manifold adapted tobe received within said housing, said manifold having an inlet incommunication with said fuel inlet means in said housing and a pluralityof apertures spaced in axial alignment with said pockets of saidserrated configured chamber whereby fuelenters said chamber through saidpockets parallel to the axis of said chamber; and, each V-shaped pocketincludes two flanks, at least one of said flanks having at least oneaperture therein whereby air entering said plenum through said air inletin said housing passes through said aperture in said flank transverselyof said fuel passing through said V- shaped pocket.

2. The gas-fired furnace of claim 1 wherein each of said V-shapedpockets is in communication with an aperture in said gas ring manifold.

3. The gas fired furnace of claim 1 wherein said chamber iscylindrically shaped.

4. The gas-fired furnace of claim 1 including a plate disposed betweensaid serrated chamber and said gas ring manifold, said plate havingapertures therein in axial alignment with said apertures in said gasring manifold.

5. The gas-fired furnace of claim 4 wherein said plate includes at leastone aperture therein communicating with said plenum whereby additionalcombustion air passes through said chamber parallel to the axis of saidchamber.

i i i

1. In a gas-fired furnace, a gas burner assembly comprising: a burner housing having fuel and air inlet means and an outlet, said housing defining a plenum therein; a longitudinally extending chamber of serrated configuration adapted to be received within said housing, said chamber having a plurality of generally V-shaped pockets therein, each pocket being defined by each serration; a gas ring manifold adapted to be received within said housing, said manifold having an inlet in communication with said fuel inlet means in said housing and a plurality of apertures spaced in axial alignment with said pockets of said serrated configured chamber whereby fuel enters said chamber through said pockets parallel to the axis of said chamber; and, each V-shaped pocket includes two flanks, at least one of said flanks having at least one aperture therein whereby air entering said plenum through said air inlet in said housing passes through said aperture in said flank transversely of said fuel passing through said V-shaped pocket.
 2. The gas-fired furnace of claim 1 wherein each of said V-shaped pockets is in communication with an aperture in said gas ring manifold.
 3. The gas fired furnace of claim 1 wherein said chamber is cylindrically shaped.
 4. The gas-fired furnace of claim 1 including a plate disposed between said serrated chamber and said gas ring manifold, said plate having apertures therein in axial alignment with said apertures in said gas ring manifold.
 5. The gas-fired furnace of claim 4 wherein said plate includes at least one aperture therein communicating with said plenum whereby additional combustion air passes through said chamber parallel to the axis of said chamber. 